Patent literature 1 discloses a millimeter wave Low Temperature Co-fired Ceramics (LTCC) package. The LTCC package includes a dielectric layer, a probe formed on the dielectric layer, and a monolithic microwave integrated circuit (MMIC). The probe is connected to a pad of the MMIC via a microstrip. The dielectric layer covers the whole part of an opening part of a waveguide.
Patent literature 2 discloses a microwave integrated circuit multi-chip module. This module includes a package substrate formed of a material having a dielectric property and a plurality of MMICs mounted on the package substrate. The package substrate includes a blind rectangular cavity opened in its back surface. The rectangular cavity does not reach the front surface of the package substrate. The package substrate also has a microstrip antenna provided at a position corresponding to the rectangular cavity on the front surface of the package substrate. The package substrate includes a plurality of through via holes around the rectangular cavity. The rectangular cavity and the plurality of through via holes constitute a waveguide part.